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Most clinical microbiology laboratories have replaced toxin immunoassay (EIA) alone with multistep testing (MST) protocols or nucleic acid amplification testing (NAAT) alone for the detection of C. difficile.
Study the effect of changing testing strategies on C. difficile detection and strain diversity.
A Veterans’ Affairs hospital.
Initially, toxin EIA testing was replaced by an MST approach utilizing a glutamate dehydrogenase (GDH) and toxin EIA followed by tcdB NAAT for discordant results. After 18 months, MST was replaced by a NAAT-only strategy. Available patient stool specimens were cultured for C. difficile. Restriction endonuclease analysis (REA) strain typing and quantitative in vitro toxin testing were performed on recovered isolates.
Before MST (toxin EIA), 79 of 708 specimens (11%) were positive, and after MST (MST-A), 121 of 517 specimens (23%) were positive (P < .0001). Prior to NAAT-only testing (MST-B), 80 of the 490 specimens (16%) were positive by MST, and after NAAT-only testing was implemented, 67 of the 368 specimens (18%) were positive (P = nonsignificant). After replacing toxin EIA testing, REA strain group diversity increased (8, 13, 13, and 10 REA groups in the toxin EIA, MST-A, MST-B, and NAAT-only periods, respectively) and in vitro toxin concentration decreased. The average log10 toxin concentration of the isolates were 2.08, 1.88, 1.20 and 1.55 ng/mL for the same periods, respectively.
MST and NAAT had similar detection rates for C. difficile. Compared to toxin testing alone, they detected increased diversity of C. difficile strains, many of which were low toxin producing.
To determine the impact of recurrent Clostridium difficile infection (RCDI) on patient behaviors following illness.
Using a computer algorithm, we searched the electronic medical records of 7 Chicago-area hospitals to identify patients with RCDI (2 episodes of CDI within 15 to 56 days of each other). RCDI was validated by medical record review. Patients were asked to complete a telephone survey. The survey included questions regarding general health, social isolation, symptom severity, emotional distress, and prevention behaviors.
In total, 119 patients completed the survey (32%). On average, respondents were 57.4 years old (standard deviation, 16.8); 57% were white, and ~50% reported hospitalization for CDI. At the time of their most recent illness, patients rated their diarrhea as high severity (58.5%) and their exhaustion as extreme (30.7%). Respondents indicated that they were very worried about getting sick again (41.5%) and about infecting others (31%). Almost 50% said that they have washed their hands more frequently (47%) and have increased their use of soap and water (45%) since their illness. Some of these patients (22%–32%) reported eating out less, avoiding certain medications and public areas, and increasing probiotic use. Most behavioral changes were unrelated to disease severity.
Having had RCDI appears to increase prevention-related behaviors in some patients. While some behaviors are appropriate (eg, handwashing), others are not supported by evidence of decreased risk and may negatively impact patient quality of life. Providers should discuss appropriate prevention behaviors with their patients and should clarify that other behaviors (eg, eating out less) will not affect their risk of future illness.
U.S. dairy production has been consolidating into large-scale confinement operations. Large numbers of small- to medium-scale dairies have disappeared in the last two decades, and many more are disappearing. This article analyzes small- to medium-scale dairy operations in Maryland during 1995–2009 for changes in technology and efficiency through a novel two-stage DEA approach to examine productivity changes. Conventional confinement dairy operations and management-intensive grazing dairies are analyzed separately. The results show that both dairy systems have become more productive on the technological frontiers, yet the rate of technical change for graziers was less than half the rate for confinement.
We investigated the perceived value of government programs on early-childhood development as a means of reducing childhood poverty. We incorporated preferences for the process as well as the outcome by developing two stated-preference survey instruments. One survey directly elicited respondents’ willingness to pay specifically for high-quality, intensive, early-childhood development programs at federal and state levels. A second survey elicited respondents’ preferences for increasing or decreasing taxes and reallocating expenditures between other government programs and early-childhood programs. We found that respondents cared greatly about how childhood poverty was reduced, not just reducing poverty per se. The perceived effectiveness of a program and ideological perspective were found to be important determinants of preferences for a poverty-reduction program. Respondents across all groups, including conservatives and respondents who perceived the effectiveness of early-childhood programs to be low, were not in favor of reducing the early-childhood program.
The impact of community-associated Clostridium difficile infection (CA-CDI) on patients with spinal cord injuries and disorders (SCI/Ds) is not fully understood. We examined CA-CDI cases among veterans with SCI/D, comparing them with community-onset, healthcare facility-associated (CO-HCFA) cases. Generally, patients with CA-CDI had less comorbidity, less severe CDI, and lower likelihood of antibiotic exposure.
This study determined whether surrogate organisms can predict activity against Clostridium difficile spores and compared the efficacy of hand hygiene preparations against C. difficile. Our data suggest that surrogate organisms were not predictive of C. difficile spore removal. Four preparations were significantly more effective than tap water at removing C. difficile.
To describe characteristics of Clostridium difficile infection (CDI) and markers of severe CDI among patients with hematologic malignancies.
Tertiary care teaching hospital.
Patients and Methods.
Inpatients with hematologic malignancies and CDI were age and time matched with 2 control inpatients without hematologic malignancies. Chart reviews were performed, and C. difficile isolates were strain typed.
Case patients (n = 41) and control patients (n = 82) patients were different in respect to receipt of immunosuppressive agents within 2 months (92.7% vs 25.6%; P < .0001); neutropenia within 2 months (75.6% vs 3.7%; P < .0001) and mean (± standard deviation) white blood cell (WBC) count at diagnosis (4.9 ± 14.1 vs 11.8 ± 6.8 × 103 cells/mL; P = .0002); baseline mean creatinine level (0.89 ± 0.1 vs 1.6 ± 2.4 mg/dL; P = .003), mean creatinine level at diagnosis (0.83 ± 0.4 vs 1.85 ± 1.9 mg/dL; P = .004), and creatinine increases of 1.5 times over baseline (2.4% vs 15.1%; P = .02). Immunosuppressive agents and creatinine level remained significant in multivariable analysis (P = .03 for both variables). Severity correlated with mortality when measured by alternate severity criteria but not when measured by the Society for Healthcare Epidemiology of America/Infectious Diseases Society of America criteria, which are based solely on WBC count and creatinine elevation. The prevalence of the epidemic BI/NAP1/027 strain was similar in both groups.
Patients with hematologic malignancies had lower creatinine levels at the time of CDI diagnosis compared with control patients. WBC counts also tended to be lower in case patients. CDI severity criteria based on WBC count and creatinine level may not be applicable to patients with hematologic malignancies.
Describe the clinical and molecular epidemiology of incident Clostridium difficile infection (CDI) cases in Chicago area acute healthcare facilities (HCFs).
Design and Setting.
Laboratory, clinical, and epidemiologic information was collected for patients with incident CDI who were admitted to acute HCFs in February 2009. Stool cultures and restriction endonuclease analysis typing of the recovered C. difficile isolates was performed.
Two hundred sixty-three patients from 25 acute HCFs.
Acute HCF rates ranged from 2 to 7 patients with CDI per 10,000 patient-days. The crude mortality rate was 8%, with 20 deaths occurring in patients with CDI. Forty-two (16%) patients had complications from CDI, including 4 patients who required partial, subtotal, or total colectomy, 3 of whom died. C. difficile was isolated and typed from 129 of 178 available stool specimens. The BI strain was identified in 79 (61%) isolates. Of patients discharged to long-term care who had their isolate typed, 36 (67%) had BI-associated CDI.
Severe disease was common and crude mortality was substantial among patients with CDI in Chicago area acute HCFs in February 2009. The outbreak-associated BI strain was the predominant endemic strain identified, accounting for nearly two-thirds of cases. Focal HCF outbreaks were not reported, despite the presence of the BI strain. Transfer of patients between acute and long-term HCFs may have contributed to the high incidence of BI cases in this investigation.
Objective: Conventional wisdom suggests that parasites evolve increased host specialization over time. Host specificity, which describes the number of host species parasitized, is one aspect of host specialization. Recent studies of vertebrate parasites indicate that highly host-specific parasite lineages are not, in fact, evolutionary dead ends; host generalists can evolve from host specialists.
Methods: Using phylogenetic reconstruction methods, we evaluate these patterns in the body lice (Insecta: Phthiraptera) of pigeons and doves, which are permanent ectoparasites that complete their entire life cycle on the body of the host.
Results: We find that species of body lice that parasitize more than one species of host (generalists) are invariably derived from lice parasitizing only one species of host (specialists). A previous study of the wing lice of pigeons and doves also found that generalists were derived from specialists, and that these changes were correlated with the presence of a potentially competing species of wing louse on the same host. For body lice we did not find such a correlation with competition. Instead, the evolution of host generalists in body lice was correlated with host ecology. When we compared body lice that parasitize terrestrial versus arboreal hosts, we found that the evolution of host generalists was associated with terrestrial hosts. In contrast, wing lice showed no correlation between the evolution of generalists and host ecology.
Conclusion: The correlation in body lice suggests that dispersal between host species may occur via the ground. This, in turn, suggests that body lice may fall to the ground more often than wing lice. To test this hypothesis, we conducted an experiment to compare the rate at which body and wing lice are dislodged from the bodies of preening pigeons. Interestingly, our results showed that body lice are dislodged four times more often than wing lice. Therefore, species of terrestrial doves are far more likely to encounter body lice than wing lice on the ground.
Alcohol-based hand rubs (ABHRs) are an effective means of decreasing the transmission of bacterial pathogens. Alcohol is not effective against Clostridium difficile spores. We examined the retention of C. difficile spores on the hands of volunteers after ABHR use and the subsequent transfer of these spores through physical contact.
Nontoxigenic C. difficile spores were spread on the bare palms of 10 volunteers. Use of 3 ABHRs and chlorhexidine soap-and-water washing were compared with plain water rubbing alone for removal of C. difficile spores. Palmar cultures were performed before and after hand decontamination by means of a plate stamping method. Transferability of C. difficile after application of ABHR was tested by having each volunteer shake hands with an uninoculated volunteer.
Plain water rubbing reduced palmar culture counts by a mean (± standard deviation [SD]) of 1.57 ± 0.11 log10 colony-forming units (CFU) per cm2, and this value was set as the zero point for the other products. Compared with water washing, chlorhexidine soap washing reduced spore counts by a mean ( ± SD) of 0.89 ± 0.34 log10 CFU per cm2; among the ABHRs, Isagel accounted for a reduction of 0.11 ± 0.20 log10 CFU per cm2 (P = .005), Endure for a reduction of 0.37 ± 0.42 log10 CFU per cm2 (P = .010), and Purell for a reduction of 0.14 ± 0.33 log10 CFU per cm2 (P = .005). There were no statistically significant differences between the reductions achieved by the ABHRs; only Endure had a reduction statistically different from that for water control rubbing (P = .040). After ABHR use, handshaking transferred a mean of 30% of the residual C. difficile spores to the hands of recipients.
Hand washing with soap and water is significantly more effective at removing C. difficile spores from the hands of volunteers than are ABHRs. Residual spores are readily transferred by a handshake after use of ABHR.
Since publication of the Society for Healthcare Epidemiology of America position paper on Clostridium difficile infection in 1995, significant changes have occurred in the epidemiology and treatment of this infection. C. difficile remains the most important cause of healthcare-associated diarrhea and is increasingly important as a community pathogen. A more virulent strain of C. difficile has been identified and has been responsible for more-severe cases of disease worldwide. Data reporting the decreased effectiveness of metronidazole in the treatment of severe disease have been published. Despite the increasing quantity of data available, areas of controversy still exist. This guideline updates recommendations regarding epidemiology, diagnosis, treatment, and infection control and environmental management.
Fracture surfaces of Zr-based bulk metallic glasses of various compositions tested in the as-cast and annealed conditions were analyzed using scanning electron microscopy. The tougher samples have shown highly jagged patterns at the beginning stage of crack propagation, and the length and roughness of this jagged pattern correlate well with the measured fracture toughness values. These jagged patterns, the main source of energy dissipation in the sample, are attributed to the formation of shear bands inside the sample. This observation provides strong evidence of significant “plastic zone” screening at the crack tip.
Dale Van Stempvoort, National Water Research Institute, PO Box 5050, Burlington ON, Canada L7R 4A6,
Kevin Biggar, BGC Engineering, Inc., 207, 5140–82 Avenue, Edmonton, Alberta, Canada T6B OE6,
Dennis M. Filler, Dept. of Civil and Environmental Engineering, University of Alaska Fairbanks, PO Box 755900, Fairbanks AK 99775, USA,
Ronald A. Johnson, Dept. of Mechanical Engineering, Institute of Northern Engineering Energy Research Center, University of Alaska Fairbanks, PO Box 755910, Fairbanks AK 99775–5910, USA,
Ian Snape, Environmental Protection and Change Program, Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia,
Kate Mumford, Particulate Fluids Processing Centre (ARC Special Research Centre), Department of Chemical and Biomolecular Engineering, University of Melbourne, Victoria 3010, Australia,
William Schnabel, Golder Associates, 1346 West Arrowhead Road, Duluth MN 55811, USA,
Steve Bainbridge, Contaminated Sites Program, Division of Spill Prevention and Response, Department of Environmental Conservation, 610 University Avenue, Fairbanks AK 99709–3643, USA
In this book, current scientific knowledge and practical experiences with bioremediation of petroleum-contaminated soils in cold regions are reviewed and compiled. We now more fully understand the inter-relationships between cold temperatures, soil and water properties, and biological processes. This aids decision making about practical remediation treatment for petroleum-contaminated sites in cold regions. Landfarming and enhanced bioremediation schemes have emerged as viable soil treatment methods that offer a number of advantages over other methods. Nevertheless, work still needs to be done to optimize these methods, and with regards to evaluating phytoremediation and rhizosphere enhancement potentials for cold soils.
Two emerging technologies have been identified that could offer significant cost savings; low-cost heating and controlled-release nutrient systems are described briefly here (see also Chapter 8). In addition, natural attenuation has received little rigorous evaluation for use in cold soils. The main limitation for natural attenuation in cold regions is the low rate of degradation, coupled with off-site migration that can be relatively rapid in soils or gravel pads that have a poor adsorption capacity. Permeable reactive barriers are one groundwater treatment technology that could buy time for slower in situ techniques such as natural attenuation to take place. An outline of emerging permeable-reactive barrier technology is presented here, although full-scale trials are not yet complete. It is possible that such in situ techniques, when coupled with aeration, sparging and biostimulation could offer methods for groundwater treatment in cold regions.